Improve terminal renderer recovery

packages/app/src/terminal/runtime/terminal-emulator-runtime.ts

@@ -158,6 +158,7 @@ export class TerminalEmulatorRuntime {
       convertEol: false,
       cursorBlink: true,
       cursorStyle: "bar",
+      customGlyphs: true,
       fontFamily: DEFAULT_TERMINAL_FONT_FAMILY,
       fontSize: 13,
       lineHeight: 1.0,
@@ -173,6 +174,7 @@ export class TerminalEmulatorRuntime {
     const fitAddon = new FitAddon();
     const unicode11Addon = new Unicode11Addon();
     let webglAddon: WebglAddon | null = null;
+    let imageAddon: ImageAddon | null = null;
     terminal.loadAddon(fitAddon);
     terminal.loadAddon(unicode11Addon);
     terminal.loadAddon(
@@ -195,34 +197,46 @@ export class TerminalEmulatorRuntime {
       // Ignore if unicode API isn't available in this build/runtime.
     }
 
-    // Prefer GPU rendering when available. This tends to reduce visible seams in block characters
-    // and improves scroll performance, but must gracefully fall back on platforms without WebGL.
+    const disposeImageAddon = (): void => {
+      try {
+        imageAddon?.dispose();
+      } catch {
+        // ignore
+      }
+      imageAddon = null;
+    };
+    const disposeWebglRenderer = (): void => {
+      if (!webglAddon) {
+        return;
+      }
+      try {
+        webglAddon.dispose();
+      } catch {
+        // ignore
+      }
+      webglAddon = null;
+      disposeImageAddon();
+      // WebGL and DOM renderers can have different cell dimensions.
+      this.fitAndEmitResize?.(true);
+    };
+
     let webglAddonRaf: number | null = requestAnimationFrame(() => {
       webglAddonRaf = null;
       try {
+        disposeWebglRenderer();
         webglAddon = new WebglAddon();
         webglAddon.onContextLoss(() => {
-          try {
-            webglAddon?.dispose();
-          } catch {
-            // ignore
-          }
-          webglAddon = null;
-          // Force a refresh after context loss to avoid visual corruption.
-          try {
-            terminal.refresh(0, terminal.rows - 1);
-          } catch {
-            // ignore
-          }
+          disposeWebglRenderer();
         });
         terminal.loadAddon(webglAddon);
+        imageAddon = new ImageAddon();
+        terminal.loadAddon(imageAddon);
+        this.fitAndEmitResize?.(true);
       } catch {
-        webglAddon = null;
+        disposeWebglRenderer();
       }
     });
 
-    terminal.loadAddon(new ImageAddon());
-
     // Suppress terminal query responses — the server-side headless xterm handles these.
     // Without this, xterm.js generates DA/CPR responses via onData that feed back
     // to the PTY as visible text.
@@ -451,12 +465,8 @@ export class TerminalEmulatorRuntime {
           cancelAnimationFrame(webglAddonRaf);
           webglAddonRaf = null;
         }
-        try {
-          webglAddon?.dispose();
-        } catch {
-          // ignore
-        }
-        webglAddon = null;
+        disposeWebglRenderer();
+        disposeImageAddon();
       },
       disposeTerminal: () => {
         terminal.dispose();